Mapping of quantitative adult plant field resistance to leaf rust and stripe rust in two European winter wheat populations reveals co-location of three QTL conferring resistance to both rust pathogens

Key message We detected several, most likely novel QTL for adult plant resistance to rusts. Notably three QTL improved resistance to leaf rust and stripe rust simultaneously indicating broad spectrum resistance QTL. Abstract The rusts of wheat (Puccinia spp.) are destructive fungal wheat diseases. The deployment of resistant cultivars plays a central role in integrated rust disease management. Durability of resistance would be preferred, but is difficult to analyse. The Austrian winter wheat cultivar Capo was released in the 1989 and grown on a large acreage during more than two decades and maintained a good level of quantitative leaf rust and stripe rust resistance. Two bi-parental mapping populations: Capo × Arina and Capo × Furore were tested in multiple environments for severity of leaf rust and stripe rust at the adult plant stage in replicated field experiments. Quantitative trait loci associated with leaf rust and stripe rust severity were mapped using DArT and SSR markers. Five QTL were detected in multiple environments associated with resistance to leaf rust designated as QLr.ifa-2AL, QLr.ifa-2BL, QLr.ifa-2BS, QLr.ifa-3BS, and QLr.ifa-5BL, and five for resistance to stripe rust QYr.ifa-2AL, QYr.ifa-2BL, QYr.ifa-3AS, QYr.ifa-3BS, and QYr.ifa-5A. For all QTL apart from two (QYr.ifa-3AS, QLr.ifa-5BL) Capo contributed the resistance improving allele. The leaf rust and stripe rust resistance QTL on 2AL, 2BL and 3BS mapped to the same chromosome positions, indicating either closely linked genes or pleiotropic gene action. These three multiple disease resistance QTL (QLr.ifa-2AL/QYr.ifa-2AL, QLr.ifa.2BL/QYr.ifa-2BL, QLr.ifa-3BS/QYr.ifa.3BS) potentially contribute novel resistance sources for stripe rust and leaf rust. The long-lasting resistance of Capo apparently rests upon a combination of several genes. The described germplasm, QTL and markers are applicable for simultaneous resistance improvement against leaf rust and stripe rust. © 2014 The Author(s)

Molecular genetic analysis of durable adult plant leaf rust resistance of the Austrian winter wheat cultivar "Capo"

Braunrost ist eine durch Puccinia triticina hervorgerufene, weit verbreitete Pilzkrankheit von Weizen, die zu beträchtlichen Ertragsverlusten führt. Capo ist eine wichtige österreichische Winterweizensorte, die gering anfällig für P. triticina ist, obwohl sie seit mehr als 20 Jahren großflächig angebaut und häufig in Zuchtprogrammen verwendet wird. Frühere Tests haben gezeigt, dass Capo das Resistenzgen Lr13 (Lr für leaf rust) enthält, das allein aber in großen Teilen Europas nicht mehr länger wirksam ist. Ziel der vorliegenden Untersuchung war es, genauere Kenntnisse über die Vererbung der quantitativen und dauerhaften Resistenz im Erwachsenenstadium von Capo zu erlangen. Von Capo abgeleitete Populationen wurden in künstlich inokulierten Feldversuchen auf mehreren Standorten mehrjährig getestet. Die Population Isengrain/Capo wurde mit molekularen Markern genetisch charakterisiert und eine Kopplungskarte erstellt. In einem ersten Validierungsschritt wurden einige Marker auch für eine zweite Population eingesetzt. Es wurden mehrere quantitativ wirkende Effekte (QTL für quantitative trait loci) entdeckt. Der wirksamste von Capo vererbte QTL wurde am kurzen Arm von Chromosom 3B (Marker Xbarc75) kartiert und erklärte bis zu 15 % der phänotypischen Varianz. Dieser QTL konnte auch in der zweiten Population gefunden werden und war auch gegenüber Gelbrost (Puccinia striiformis f. sp. tritici) wirksam. Der wirksamste QTL stammte von der Sorte Isengrain und erklärte bis zu 50 % der phänotypischen Varianz am langen Arm von Chromosom 7B. Dieser QTL könne ein Allel des Rostresistenzgenes Lr14 sein. Die entdeckten genetischen Marker für diese neuen Resistenz-QTL gegen Braunrost sind die ersten, die für mitteleuropäisches Zuchtmaterial geeignet sind. Markergestützte Selektion beschleunigt die Resistenzzüchtung und ermöglicht somit die Entwicklung von Sorten mit kombinierter und dadurch dauerhafter Braunrostresistenz.Leaf rust caused by Puccinia triticina (formerly Puccinia recondita f. sp. tritici) is a commonly occurring fungal wheat disease and leads to significant yield loss. Capo is an important Austrian winter wheat cultivar hardly susceptible to P. recondita despite extensive cultivation and wide use in breeding programs for more than 20 years. Previous tests have shown that Capo carries Lr13, a leaf rust resistance (Lr) gene which on its own is no longer effective against leaf rust in large parts of Europe. The aim of the study at hand was to elucidate the genetics of Capos quantitative and durable adult plant resistance by means of molecular mapping. Capo derived populations were tested for leaf rust resistance in artificially inoculated field experiments at several locations during three to six seasons. The Isengrain/Capo population was genotyped with molecular markers and a linkage map was calculated. In a first validation step some of the markers were also applied to a second population. In the Isengrain/Capo population several quantitative trait loci (QTL) for leaf rust were identified. The most effective Capo derived QTL was located on the short arm of chromosome 3B (marker Xbarc75) and accounted for up to 15 % of the phenotypic variance. This QTL was also detected in the second population and furthermore effective against yellow rust (Puccinia striiformis f. sp. tritici). The most effective QTL originated from the cultivar Isengrain and contributed up to 50 % of the phenotypic variance. The most likely position is the marker interval XS26M14_4Xwmc557.1 on the long arm of chromosome 7B. This QTL is possibly an allele of the Lr14 rust resistance gene. The identified genetic markers for tagging these new leaf rust resistance QTL are the first suitable for Central European breeding material. Marker-assisted selection accelerates resistance breeding and enables the development of lines with combined and thus durable leaf rust resistance.eingereicht von: Lydia MatiaschAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersZsfassung in dt. SpracheWien, Univ. für Bodenkultur, Diss., 2014OeBB(VLID)193130